I have to highly recommend this game. It is done in the guise of Portal with testing chambers that contain elaborate puzzles revolving around singular exit points. Unlike Portal, it has a very deep story that discusses the ethical boundaries between man and machine. T.O.M., an advanced AI with a wonderful voice actor that sounds like Jeremy Irons, is a fantastic character that just keeps rewarding the player with very well written dialogue. I won't spoil the big twist of the game, but T.O.M. has a role in the puzzle mechanics that I believe outdoes Portal. The game just throws so many new components at the players and the puzzles are quite nicely done. It's 20 bucks at the moment, which should be going down eventually. You definitely won't get 20 hours out of it, but the story is worth your time. One of my favorite games, to date.
Also, the big selling point of the game is that it advertises "these puzzles cannot be solved by a computer." Not sure how true that is, but there you have it.
